One of Scotland’s most significant seabird colonies has experienced an “apocalyptic” decline in numbers, according to the country’s largest nature conservation charity.

The Royal Society for the Protection of Birds (RSPB) said the sharp drop off in the seabird population in Shetland was unprecedented. Scientists have attributed the downward trend to a series of factors, including climate change, declining food sources and the scourge of plastic pollutants.

The charity, which runs a nature reserve at Sumburgh Head on the southern tip of the Shetland mainland, warned the plummeting numbers were “utterly tragic”

Helen Moncrieff, RSPB’s area manager for Shetland, said at the society’s sites in Dalsetter and Troswick there were only 110 Arctic terns last week, compared with around 9,000 at the turn of the millennium.

She said: “In the past, Sumburgh Head was brimming with birds and the air was thick with the smell of guano. The place was covered with colonies of puffins, kittiwakes, fulmars and guillemots. There were thousands and thousands of birds and visitors were guaranteed a sight of puffins. Today they have to be very patient. At the same time, guillemots have halved in numbers. It is utterly tragic.”

Figures show while there were 33,000 puffins on the island in the spring of 2000, the population stood at just 570 last year. There are no signs of any recovery in 2018, although it is still early in the season.

Shetland’s kittiwake population fell from more than 55,000 in 1981 to just 5,000 in 2011. Observers believe those numbers have declined even further. Dr Euan Dunn, RSPB’s principal marine advisor, said: “These are apocalyptic numbers. We are seeing something very dramatic happening, something that has never occurred in the history of ornithology up there.”

According to Dr Dunn, rising sea temperatures in the North Sea and North Atlantic have impacted on the ability of the seabirds to find food sources. He said: “This warming seems to be affecting the availability of plankton at the time when sand eels produce their larvae. There is less plankton and the larvae grow less well and survive less well.”

One puffin monitored by the RSPB was found to have flown more than 248 miles in order to find food. Dr Dunn added: “That is more than ten times further than we thought they were flying..”